Scant Support for Flu Vaccines in Older Patients

Action Points

Explain to patients that a review of the medical literature found only modest evidence to support vaccination of older people against influenza.

Note that the review does not prove that vaccinatiion of older patients is not worthwhile.

The practice of targeting influenza vaccine to older people has only poor-quality supporting evidence that fails to show a clear benefit or harm, authors of a systematic review concluded.

The only randomized, controlled trial of acceptable quality "seemed" to show a beneficial effect of vaccination against influenza symptoms but lacked statistical power to examine the effect on complications.

"The available evidence is of poor quality and provides no guidance regarding the safety, efficacy, or effectiveness of influenza vaccines for people ages 65 years or older," Tom Jefferson, MD, of the Cochrane Collaboration in Rome, and colleagues wrote in an article published in The Cochrane Library.

"To resolve the uncertainty, an adequately powered publicly funded randomized, placebo-controlled trial run over several seasons should be undertaken."

Health officials worldwide recommend influenza vaccination for people 65 and older because of that population's increased risk for complications, hospitalization, and death from influenza. The H1N1 influenza pandemic has heightened interest in vaccines and their safety and efficacy, the authors noted.

Accurate information about the effects of influenza vaccine is necessary for informed decisions about alternative strategies, they continued. Of the two previously published reviews of influenza vaccine in older patients, one is 15 years old and does not include recent evidence (Ann Intern Med 1995; 123: 518-27). The other review included a limited number of studies and had several methodologic weaknesses that could affect conclusions (Vaccine 2002; 20: 1831-36).

In an effort to update information on the issue, Jefferson and colleagues performed a systematic review of the literature about vaccination against influenza in older patients. They extracted randomized controlled trials, quasi-randomized controlled trials, and cohort and case-control studies of vaccine efficacy against influenza or influenza-like illness or safety.

The search identified 75 studies and 100 data sets. The investigators included 68 studies in their assessment of efficacy/effectiveness, and eight were included in the safety assessment (one study considered in both analyses). Cohort studies accounted for 51 of the total, and the analysis included five randomized controlled trials.

The randomized controlled trials were published from 1969 through 2004. Collectively, the studies exhibited such extensive heterogeneity that "no firm conclusions can be drawn from this body of evidence," the authors wrote. A meta-analysis of two trials suggested inactivated vaccine's superiority to placebo against influenza-like illness among older people living in communities with high viral circulation (point estimate 43%). Three of the trials suggested vaccines' effectiveness against influenza (point estimate 58%).

Summarizing the overall results of their review and analysis, the authors found that "the effectiveness of trivalent inactivated influenza vaccines in elderly individuals is modest, irrespective of setting, outcome, population, and study design."

The scarcity of randomized controlled trials made interpretation of the data difficult, at best, they noted. The quality of nonrandomized controlled trials, which accounted for most of the data, was of particular concern.

"Until such time as the role of vaccines for preventing influenza in the elderly is clarified, more comprehensive and effective strategies for the control of acute respiratory infections should be implemented," they wrote in conclusion.

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